In a typical cellular radio system, wireless terminals (also referred to as user equipment unit nodes or UEs, and/or mobile terminals/stations) communicate via a radio access network (RAN) with one or more core networks. The RAN covers a geographical area which is divided into cell areas, with each cell area being served by a radio base station (also referred to as a RAN node, a “NodeB”, and/or enhanced NodeB “eNodeB”). A cell area is a geographical area where radio coverage is provided by the base station equipment at a base station site. The base stations communicate through radio communication channels with wireless terminals within range of the base stations.
The 3GPP (3rd Generation Partnership Project) 22.011 standard describes access control (AC) for wireless/mobile terminals in a network. Under certain circumstances, it may be useful/necessary to prevent a wireless/mobile terminal (UE) in a wireless communications network from accessing the network. In an E-UTRAN (Evolved-UTRAN or Evolved Universal Terrestrial Radio Access Network) network, for example, access control may be useful/necessary to vary the probability of wireless/mobile terminals accessing the network for purposes of: (a) congestion control, (b) emergency situations, and/or (c) other special situations.
All wireless/mobile terminals (UEs) may be members of one of ten randomly allocated wireless/mobile terminal populations, defined as access classes 0 to 9. The access class number of a wireless/mobile terminal (UE) may be stored in memory (e.g., in a SIM or subscriber identity module, in a USIM or Universal subscriber identity module, etc.) of the wireless/mobile terminal (UE). In addition, some wireless/mobile terminals (UEs) may be members of one or more of five special categories (access classes 11 to 15), also saved in memory (e.g., in a SIM, USIM, etc.). Wireless/mobile terminals (UEs) that are members of these special categories may be given higher access priority and may be categorized as follows:
ClassDescription15PLMN (Public Land Mobile Network) Staff;14Emergency Services;13Public Utilities (e.g., water/gas suppliers);12Security Services; and11Reserved for PLMN use.Access class 10 may be provided for emergency calls. Requirements for E-UTRAN enhanced access control are discussed as follows.
In an E-UTRAN network, the serving network broadcasts mean durations of access control (e.g., time durations) and barring rates (e.g., percentage/decimal values) that are commonly applied to wireless/mobile terminals (UEs) of access classes 0-9. A barring rate defines the probability that a wireless/mobile terminal (UE) will be granted access to the network if the wireless/mobile terminal attempts to access the network, and a mean duration of access control defines a period of time after a barred access attempt before the wireless/mobile terminal will be allowed a next attempt to access to the network. A combination of this mechanism(s) and a mechanism(s) of UMTS (Universal Mobile Telecommunications System) may be applied for access classes 11-15.
An E-UTRAN network may support access control based on a type of access attempt (i.e., a wireless/mobile terminal originating data or a wireless/mobile terminal originating signaling), in which indications to the wireless/mobile terminals (UEs) are broadcast to guide behavior of the wireless/mobile terminal (UE). An E-UTRAN network forms combinations of access control based on a type of access attempt (e.g., wireless/mobile terminal originating, wireless/mobile terminal terminating, location registration, etc.). The mean duration of access control and the barring rate may be broadcast for each type of access attempt (i.e., wireless/mobile terminal originating data or wireless/mobile terminal originating signaling).
The wireless/mobile terminal (UE) determines its barring status with the information provided from the serving network, and the wireless/mobile terminal (UE) performs the access attempts according to the determined barring status. More particularly, the wireless/mobile terminal (UE) may draw/generate a uniform random number between 0 and 1 when initiating a network access attempt, and the wireless/mobile terminal (UE) compares this random number with the current barring rate to determine whether the network access attempt is barred or not. When the random number is lower than the current barring rate and the type of access attempt is indicated allowed, then the network access attempt is allowed. Otherwise (i.e., when the random number is greater than the current barring rate), the network access attempt is not allowed (i.e., the network access attempt is barred). If the network access attempt is not allowed (i.e., the network access attempt is barred), further network access attempts of the same access type of the same wireless/mobile terminal (UE) are barred for a period of time that is calculated based on the mean duration of access control provided by the network and the random number drawn by the UE.
The 3GPP standard further describes service specific access control (SSAC) for multimedia telephony (MMTel) functions to apply independent access control for telephony services for mobile originating session requests from idle-mode as follows. EPS (Evolved Packet System) provides a capability to assign a service probability factor and mean duration of access control for each of MMTel voice and MMTel video. The 3GPP standard also defines access control for circuit switched fall back (CSFB).
Extended access barring (EAB) is a mechanism for an operator(s) to control Mobile Originating access attempts from wireless/mobile terminals (UEs) that are configured for EAB to reduce/prevent overload of the access network and/or the core network. In congestion situations, for example, an operator of the network can restrict access from wireless/mobile terminals (UEs) configured for EAB while permitting access from other wireless/mobile terminals (UEs).
Future wireless/mobile networks may differentiate between different classes of services used by a same wireless/mobile terminal (UE) and between different classes wireless/mobile terminals (UEs). Accordingly, there may be interest to extend the concept of overload control to allow for such differentiation. A network operator, for example, may want to serve machine type communication (MTC) devices using access control that is different than access control used for other device types. Existing EAB mechanisms, however, may not adequately serve MTC devices for one or more of the following reasons.
MTC devices are not a uniform category of devices. MTC devices, for example may be used in diverse situations providing differing service characteristics for different applications, such as a smart grid applications, automotive communication applications, sensor network applications, etc. MTC devices may also benefit from characterization for access classes such as Emergency Services, Security functions, PLMN staff, etc.
Networks serving MTC devices may benefit from congestion control and overload protection that is separate from the normal EAB mechanism. A network operator, for example, may not want energy meters to load the network during rush hour. A network operator may want mobile originated access from low priority sensors to be very infrequent. Current EAB mechanisms may use a single access control barring factor/rate and a single access control barring time for all classes of terminals, MTC devices, etc.
Accordingly, there continues to exist a need in the art for improved access barring control for terminals/devices communicating with a mobile wireless communications network.